I'll start though with a table summarising the opinions of only the ChiPS and MARS System, which this week highlights the changes in those Systems' team ratings relative to the start of the season.
Port Adelaide, it's clear, has been the big mover this year according to both Systems. On ChiPS, Port Adelaide has climbed 5 places and accumulated over 17 additional Rating Points (RPs), while on MARS they've climbed 6 places and netted over 14 RPs. (Bear in mind that 1 ChiPS RP does not equal 1 MARS RP, though rankings are rankings, of course.)
Despite the fact that West Coast's performances have earned them 5 RPs on ChiPS and on MARS, the Eagles' results have been more surprising to ChiPS in terms of team rankings. On ChiPS West Coast are up 4 places relative to where they were at the start of the season, while on MARS they're up by only a single place. The Gold Coast have also climbed significantly since the start of the season, up 3 places to 13th on ChiPS, and up 2 places to 14th on MARS.
The largest falls have been registered by the Roos, down 3 spots on ChiPS and 2 spots on MARS; by Sydney, down 2 spots on both; by Carlton, down 3 spots also on both; and by the Brisbane Lions, down 4 spots on ChiPS and 3 spots on MARS.
There are only two teams about whose rankings the two Systems disagree by more than a single place: Sydney, who are 9th on ChiPS and 6th on the more forgiving MARS, and St Kilda who are 15th on ChiPS and 13th on MARS.
The broad, season-long agreement between ChiPS and MARS about the level and direction of the changes in team ratings from week to week are evident in the chart below.
Broadening the view to incorporate Colley, Massey and ODM, let's first look at how these three Systems, along with ChiPS and MARS, have ranked all of the teams across the season so far.
It's clear that the levels of agreement in terms of team rankings are fairly high not just between ChiPS (the black lines) and MARS (the blue lines), but across all five Systems. The eight teams for which there is more than what might be characterised as minor disagreement are:
- Carlton (ChiPS and MARS high, Colley low)
- Essendon (Massey and ODM high)
- Gold Coast (Colley high)
- GWS (ChiPS and MARS low)
- Richmond (ChiPS and MARS high)
- St Kilda (Colley high, ChiPS low)
- Sydney (MARS high, Colley low)
- West Coast (ChiPS and MARS low)
ODM ratings, you might recall, comprise separate components for each team's defensive and offensive abilities. These components are charted below.
ODM's assessment is that the following teams have significantly better offence than defence: Adelaide, Carlton, Hawthorn, Port Adelaide and the Western Bulldogs.
Conversely, it assesses the following teams as have significantly better defence than offence: Gold Coast, Kangaroos, Melbourne, St Kilda and West Coast.
Finally, let's look at the predictive accuracy of the five Systems, giving each System a 50% record in Round 1 (since Colley, Massey and ODM have no Ratings at that point of the season) and making the simplifying assumption that each System selects the team with the higher rating going into the game, regardless of whether or not it is the home team, has better form, and so on.
The results shown here are relative to the predictive accuracy of the MARS System.
ChiPS is the only System with an accuracy superior to MARS'. It has selected the winner in two games more than MARS. Colley trails MARS by 10 tips, Massey by 5, and the ODM System trails by 9. Tips based solely on ODM's Offensive rankings trail MARS tips by 8 games, while those based solely on ODM's Defensive rankings trail MARS by 5 tips.
This year, it seems, appropriately incorporating information about the teams' 2013 performances has added significantly to predictive accuracy.